(1) Field of the Invention
The present invention relates to a purge apparatus which maintains the cleanliness of the inside of a container used for storing reticles, wafers, glass substrates and the like in manufacturing a semiconductor device.
(2) Description of the Related Art
In the manufacturing process of a semiconductor device such as an LSI, it is necessary to store wafers, glass substrates, reticles and the like such that they do not become deteriorated or degenerated. For example, the wafers need to be stored in a low oxygen state to prevent oxidization, and the reticles need to be stored in an atmosphere where water (H2O) is eliminated to suppress haze growth. Further, it is necessary to prevent particles from adhering on the wafers and the like as much as possible. Therefore, in most cases, the wafers and the like are stored in a container which is filled with clean gas that is composed of a type of gas compatible with the storage objects.
However, as in the case disclosed in Japanese Unexamined Patent Application Publication No. 2001-31212, the stored wafers may need to be sorted into several containers. In such a case, the container needs to be opened. Thus, a so-called “purge processing” is performed which introduces clean gas into the opened container and makes the internal atmosphere of the container a more positive pressure than the external atmosphere of the container, so that a high level of cleanliness can be maintained.
Further, since the reticles and the like are stored for a relatively long period of time, it is considered that storage in a container, on which purge processing is constantly performed, causes less particle contamination than storage in a sealed container. Therefore, purge apparatuses are available which can constantly provide a continuous purge to the container with clean gas.
However, even in the case where such a conventional purge apparatus is used, it is known that the wafers and the reticles being stored become contaminated with the particles on rare occasions. As a result of devoted research and effort, the inventors of the present invention have reached the finding that the particle contamination, which only rarely occurs, is caused by the purge apparatus. Furthermore, in the case where the purge apparatus is not used for a certain period of time, nozzles which discharge clean gas into the container become contaminated with the particles. When the container is purged by using the nozzles, the particles that adhered to the nozzles, while the nozzles were not in use, ingress the container, which results in contamination of the contained objects.